So nothing yet in about two weeks, any suggestions? Followed the instructions to the letter.

We saw fruiting within 5 days of planting. Make sure you follow instruction concerning how often you should mist them and the temperature your room needs to be. If it’s too cold or too dry, the mushrooms won’t fruit. Mushrooms like warmth and moisture.

After the harvest, can spores be collected from these mushrooms and reuse the kit again and again?

Yes it is possible but I did not use collected spores but rather collected mycelium and added it to new growth material(substrate.) After about a month, I had an entire new bag of oysters growing along with the original. I kept this up for about 5 months and had 4 different grow bags from the original mycelium I harvested.

About how many mushrooms grow in one kit? (I have a class of 40 students and want to make sure I would have enough for everyone)

Depends on care & environmental conditions. May grow several to 30 or more mushrooms.

On average how many flushes do you normally get?

I got two with the one kit that I did indoors. The first flush was the best. The instructions say you can also try to seed the spent culture out doors by adding it a likely spot outdoors. I put it into some compost outdoors, but haven't had any results yet.